The clever closing system on the Markill Aquarius Trinksystem means you can adapt its capacity from 2.5 litres down to 0.5 litres and open the top right up to clean thoroughly inside. The pack also comes with a dedicated tube brush so the perennial problem of bladder gunk can be easily dealt with. And when you get to your camp for the night, you can take the hose off and use the secondary stopper to turn this into a simple water container. Once filled up there is a dedicated clip to keep the mouthpiece attached to your pack, and the water tastes fresh with no hint of plastic whatsoever. But the closure system is fussier than similar models, because there’s no rigidity in the bladder. There are a number of pieces that could easily get lost, and you can’t remove the hose from the bladder without water spilling out.